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Chapter 70 - Clinical Care in Altered Environments: At High and Low Pressure and in Space

Richard E. Moon

Enrico M. Camporesi

Hyperbaric medicine began in the 19th century, when clinical improvement was observed after recompression of divers and compressed air workers with decompression sickness. Exposure of patients to hyperbaric pressure for therapeutic purposes was introduced in several large facilities. Hyperbaric air treatment in the 19th century was reported for a variety of diseases, including tuberculosis, heart failure, emphysema, bronchitis, asthma, croup, whooping cough, anemia, anorexia, dyspepsia, leukorrhea, menorrhagia, neuralgic pain, and depression. These early applications, based on vague pathophysiologic principles, suffered from an overoptimistic view of the results. ^{[1] [2]} Hyperbaric spas flourished in the early 1900s in Europe and North America. Lack of a firm physiologic

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Figure 70-1 Mobile hyperbaric operating room described by Fontaine in 1879.^[5] Nitrous oxide storage tanks can be seen under the operating table. A nitrous oxide-oxygen mixture compressed to 1.25 to 1.33 atmospheres absolute (ATA) with air was provided to the patient. Breathing air in this chamber would have provided an inspired PO₂ equivalent to 26% to 28% O₂ at 1 ATA.

An exception was the use of a mobile hyperbaric chamber for anesthesia and surgery by Fontaine.^[5] A nitrous oxide-oxygen mixture compressed to 1.25 to 1.33 atmospheres absolute (ATA) was provided to the patient ( Fig. 70-1 ). Fontaine reported that asphyxia and cyanosis, often present during normal induction of anesthesia at 1 ATA, were absent in the hyperbaric chamber. Breathing air in Fontaine's chamber would have provided an inspired PO₂ equivalent to 26% to 28% O₂ at 1 ATA. This was perhaps the first use of elevated PO₂ during anesthesia.

Until the 20th century, hyperbaric treatment involved the use of air. Use of O₂ at high pressure for the treatment of decompression sickness had previously been suggested^[6] and reported for the treatment of decompression sickness,^[7] but it remained an isolated medical curiosity. The clinical application of hyperbaric oxygen (HBO) began in the late 1950s, in parallel with an increased understanding of blood gas analysis and gas exchange physiology.

In the early 1960s, several institutions in Europe and the United States pursued investigations into the clinical efficacy of high-pressure oxygenation. A few indications, such as support of oxygenation in hyaline membrane disease of the newborn^[8] and during open heart surgery,^{[9] [10]} did not withstand the test of time: the former because of pulmonary oxygen toxicity, the latter because of the development of cardiopulmonary bypass. Indications are reviewed regularly by the Undersea and Hyperbaric Medical Society (headquarters in Kensington, MD). This medical organization publishes an extensive bibliography with a list of indications for hyperbaric oxygenation that is updated every 2 to 3 years.^[11] Laboratory and clinical data support the use of HBO for a select number of acute and chronic illnesses ( Table 70-1 ), and anesthesiologists are often called on to provide care for patients in this unusual environment.

Interest in the physiologic and medical aspects of altitude originated as a result of the mountaineering and high-altitude balloon exploits in the 19th century. This body of knowledge has become increasingly useful as the number of people flying in aircraft, traveling from low to high altitude, and living or working at higher elevations progressively increases ( Table 70-2 ). Exposure to altitude is accompanied by well-known physiologic changes and unique clinical syndromes. Significant effort has been devoted to techniques for prophylaxis and treatment of these illness in recent years. In addition, increasingly sensitive methods of monitoring oxygenation during anesthesia have led to the recognition that routine anesthetic care at even moderate altitude may require some

TABLE 70-1 -- Partial list of conditions for which hyperbaric oxygen has been used

Gas bubble disease

* Air embolism[12] [13] [14]

* Decompression sickness [12] [13]

Poisoning

* Carbon monoxide[15] [16] [17] [18]

Cyanide[19] [20]

Carbon tetrachloride[21] [22]

Hydrogen sulfide[19] [23] [24]

Infections

* Clostridial myonecrosis [25] [26] [27] [28]

* Other soft tissue necrotizing infections[28] [29] [30]

* Refractory chronic osteomyelitis[31] [32]

* Intracranial abscess [11]

Mucormycosis[33] [34]

Acute ischemia

* Crush injury[35]

* Compromised skin flaps [36] [37] [38] [39]

Chronic ischemia

* Radiation necrosis (soft tissue, radiation cystitis, and osteoradionecrosis)[40] [41] [42] [43] [44]

* Ischemic ulcers, including diabetic ulcers[45] [46]

Acute hypoxia

* Exceptional blood loss anemia (when transfusion is delayed or unavailable)[47]

Support of oxygenation during therapeutic lung lavage [48] [49]

Thermal injury

* Burns[50] [51] [52] [53] [294]

Envenomation

Brown recluse spider bite[54] [55]

*Approved by the Undersea and Hyperbaric Medical Society as an appropriate indication for HBO therapy.^[11]

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